919 research outputs found
More Communication with Less Entanglement
We exhibit the intriguing phenomena of "Less is More" using a set of
multipartite entangled states. We consider the quantum communication protocols
for the {\em exact} teleportation, superdense coding, and quantum key
distribution. We find that sometimes {\em less} entanglement is {\em more}
useful. To understand this phenomena we obtain a condition that a resource
state must satisfy to communicate a -qubit pure state with terms. We
find that the an appropriate partition of the resource state should have a
von-Neumann entropy of . Furthermore, it is shown that some
states may be suitable for exact superdense coding, but not for exact
teleportation.Comment: 7 pages, 1 tabl
Treatment of Pancreatic Cancer using Gemcitabine-loaded Superparamagnetic Iron Oxide Nanoparticles (SPIONs)
Two-qubit mixed states and teleportation fidelity: Purity, concurrence, and beyond
To explore the properties of a two-qubit mixed state, we consider quantum
teleportation. The fidelity of a teleported state depends on the resource state
purity and entanglement, as characterized by concurrence. Concurrence and
purity are functions of state parameters. However, it turns out that a state
with larger purity and concurrence, may have comparatively smaller fidelity. By
computing teleportation fidelity, concurrence and purity for two-qubit
X-states, we show it explicitly. We further show that fidelity changes
monotonically with respect to functions of parameters - other than concurrence
and purity. A state with smaller concurrence and purity, but larger value of
one of these functions has larger fidelity. These functions, thus characterize
nonlocal classical and/or quantum properties of the state that are not captured
by purity and concurrence alone. In particular, concurrence is not enough to
characterize the entanglement properties of a two-qubit mixed state
Resource state structure for controlled quantum key distribution
Quantum entanglement plays a pivotal role in many communication protocols,
like secret sharing and quantum cryptography. We consider a scenario where more
than two parties are involved in a protocol and share a multipartite entangled
state. In particular, we considered the protocol of Controlled Quantum Key
Distribution (CoQKD), introduced in the Ref. Chin. Phys. Lett. 20, 183-185
(2003), where, two parties, Alice and Bob establish a key with the cooperation
of other parties. Other parties control/supervise whether Alice and Bob can
establish the key, its security and key rate. We discuss the case of three
parties in detail and find suitable resource states. We discuss the controlling
power of the third party, Charlie. We also examine the usefulness of the new
resource states for generating conference key and for cooperative
teleportation. We find that recently introduced Bell inequalities can be useful
to establish the security of the conference key. We also generalize the
scenario to more than three parties.Comment: 11 pages, 7 figures. Close to published versio
Simulation studies of and correlation functions in pp collisions with the PYTHIA and HERWIG models
We report studies of charge-independent (CI) and charge-dependent (CD)
two-particle differential-number correlation functions, , and transverse momentum () correlation functions,
, of charged particles in
= 2.76 TeV pp collisions with the PYTHIA and HERWIG models.
Model predictions are presented for inclusive charged hadrons (), as
well as pions (), kaons (K), and (anti-)protons (/p) in the ranges , , and , with full azimuthal coverage in the range . We compare the model predictions for the strength and shape of the
and correlators as these pertain to recent
measurements by the ALICE collaboration. The and
correlation functions estimated with PYTHIA and HERWIG exhibit qualitatively
similar near-side and away-side correlation structures but feature important
differences. Our analysis indicates that comparative studies of
and correlation functions would provide valuable insight towards
the understanding of particle production in pp collisions, and by extension,
should also be useful in studies of heavy-ion collisions. Comparison of the
dependence of and could contribute, in
particular, to a better understanding and modeling of the angular ordering of
particles produced by hadronization in jets, as well as a better description of
jet fragmentation functions of identified species at low momentum fraction
.Comment: 22 pages, 24 captioned figure
Numerical Study About the Change in Flow Separation and Velocity Distribution in a 90° Pipe Bend with/without Guide Vane Conditions
A single phase, incompressible turbulent
flow through a 90º pipe bend
with/without guide vane conditions has been studied here. The present work
deals with the numerical simulation to investigate the change in flow
separation and velocity distribution at the downstream
section due to the effect of the guide
vane. The k-? turbulence model has been adopted for simulation purposes to obtain the
results. After the validation of existing experimental and numerical results, a
detailed study has been performed for three different Reynolds number and four
different positions of the guide vane. The value
of the Curvature ratio (Rc/D) has been considered
as one
factor for the present study.
The curvature ratio can be defined as the
ratio between the bend curvature radius and hydraulic diameter of the pipe. The
results obtained from the present study have been presented in graphical form.
A flow separation region has been found at the bend outlet for flow through 90º pipe bend without the guide vane. This flow separation region was
absent for the cases which dealt with
the flow through 90º pipe bend with the guide
vane. Velocity distribution at four different downstream positions for
different cases and different Reynolds numbers have been compared and reported in the present study
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